Improper inflation of tires can decrease their life expectancy by as much as 50%. Some belted tires, for example, have such sensitive limitations that merely a few pounds of air pressure, plus or minus, can drastically shorten their life spans. Some tires, such as the steel belted ones, are extremely expensive, ranging in price from $60 to $90 apiece.
Under-inflated tires can usually be detected at a glance. However, modern belted tires are designed to maintain a recommended air pressure which make them appear to be somewhat flat. As a result, many motorists over-inflate them unwittingly, unaware that it has the same basic destroying effect as under-inflating.
Over-inflation is a real problem, because it's almost impossible to detect at a glance.
All tire manufacturers are emphatic when they guarantee a tire. Their guarantees are valid only if proper specified inflation recommendations are followed. In the Mercury-Monterey, for example, a permanent plaque on the inside of the glove box door recommends 26 lbs. of air in the front tires, 28 lbs. in the rear. In other words, even with four identical tires on one car, the manufacturer regards the two-pound differential from front and rear to be essential to the life and serviceability of the tires.
But it is, as we all know, a nuisance to check tires regularly. Most people do not carry an air gauge, and, though you may occasionally get your windshield cleaned, it is almost unheard of for a service station attendant to check your tires. It's an easily overlooked task by most of us; particularly, by women, understandably so.
Automobile owners' manuals and tire manufacturers have stated that improperly inflated tires can cause a loss of up to three or more miles per gallon of gasoline. This fact was considered rather insignificant when it was first realized years ago. Today, of course, the importance of stretching a gallon of gas cannot be over-emphasized.
Various types of pressure gauges have, heretofore, been attempted to provide instantaneous indications of the nature of tire pressure within a tire as being normal, over-inflated or under-inflated. Examples of such efforts are shown in one or more of the following Patents:
U.S. Pat. No. 1,473,171--Bowden
U.S. Pat. No. 2,479,915--Eastman
U.S. Pat. No. 1,548,470--Kennedy
U.S. Pat. No. 1,807,752--Poster
U.S. Pat. No. 3,889,530--Bluem
U.S. Pat. No. 1,686,165--Morse
U.S. Pat. No. 3,886,563--Bluem
U.S. Pat. No. 3,208,425--Jousma et al
U.S. Pat. No. 3,230,968--Struby
U.S. Pat. No. 3,260,233--Bergunder